Question

the number of atom in 4.25 gram of NH3 is approximately​

Answer 1

(1 mole) that is, 17 gm NH3 has 4×6.022×10²³ atoms

So, 4.25 gms has x atoms (suppose)

So,

x = 4×6.022×10²³×4.25/17

= 6.022 × 10²³ atoms is your answer.